Sure, chances are, the truth may come out eventually but I don't believe that is always the case. You may think your SO would never ever ever do such a thing... But HOW do you know this for sure? Especially if you never go through his things or take the time to investigate?
A friend of mine was one of those women who "knew" her husband would never want another woman, let alone, look at another woman.
One day, one of her husband's co worker's, and also a friend of hers, told her that her husband wasn't being faithful. At first she was skeptical ans insulted but eventually, it got to her and she finally went through his things. Sure, enough. He was having an affair with his trainee. A physical affair, mostly. She left him..
But my question is, what if she had never got that call from her husbands co worker? What if he had got away with this & never got caught for it? I think its OK to look every once in a while, whether you trust the guy or not. Because you just NEVER KNOW